Assessment of the stability of spring wheat agrocenosis with applicationof <sup>15</sup>N and seed inoculation with biologics

The purpose of the research is to study the effect of various doses of nitrogen fertilizers and biological products on the functioning of the agroecosystem of spring wheat on dark gray forest soil. The work was performed in two tabs of the micropole experiment in 2020–2021, the scheme of which assumed the study of the following options: N45Р45К45 (background), background + Extrasol based on strain H-13 (standard), background + endophytic strain V 167, background + endophytic strain 417, N90Р45К45. When applying N45 and N90 against the background of PK, plants consume 46 and 42 % of labeled fertilizer to form a crop, respectively. When using biologics against the background of N45, the use of N-fertilizer reaches 51…53 %. 33…36 % of the applied dose of 1⁵N is fixed in the soil, when using biologics, the value of this indicator decreases to 30 %. When adding ammonium nitrate, 33…36 % of 1⁵N is lost, and when using biological products, losses are reduced to 16…18 %. The use of biological preparations for seed inoculation leads to the fact that after harvesting spring wheat, there is less mineral nitrogen in the soil by 0.47…0.51 g/m2, which indicates its best use by plants. According to the criterion of the ratio of reimobilized nitrogen to mobilized nitrogen (RI: M = 25…31 %) the agrocenosis of spring wheat, when applying nitrogen fertilizer and inoculating seeds with biologics, functions in resistance mode and the level of exposure is estimated as the maximum permissible. According to the rationing criterion, which is estimated in relation to the ratio of net mineralized nitrogen to reimobilized (NM: M = 2.24…2.98), the agrocenosis of spring wheat is in stress or resistance mode. The use of an endophytic biopreparation based on the V 417 strain leads to the fact that the agrocenosis of spring wheat functions in resistance mode at the maximum permissible level of exposure.